System and method for the re-anticoagulation of platelet rich plasma

ABSTRACT

A method for the re-anticoagulation of platelet rich plasma in a blood apheresis system includes priming the blood apheresis system with anticoagulant, such that a volume of anticoagulant is transferred to a PRP container. The method may then transfer the anticoagulant within the PRP container to a red blood cell container, and collect a volume of platelet rich plasma within the PRP container. The platelet rich plasma may be collected in a plurality of cycles. Between collection cycles, the method may transfer a portion of the volume of anticoagulant from the red blood cell container to the PRP container.

TECHNICAL FIELD

The present invention relates to systems and methods for plateletcollection, and particularly to systems and methods for there-anticoagulation of platelet rich plasma.

BACKGROUND ART

Apheresis is a procedure in which individual blood components can beseparated and collected from whole blood temporarily withdrawn from asubject. Typically, whole blood is withdrawn through a needle insertedinto a vein of the subjects arm and into a cell separator, such as acentrifugal bowl. Once the whole blood is separated into its variouscomponents, one or more of the components can be removed from thecentrifugal bowl. The remaining components can be returned to thesubject along with optional compensation fluid to make up for the volumeof the removed component. The process of drawing and returning continuesuntil the quantity of the desired component has been collected, at whichpoint the process is stopped. A central feature of apheresis systems isthat the processed but unwanted components are returned to the donor.Separated blood components may include, for example, a high densitycomponent such as red blood cells, an intermediate density componentsuch as platelets or white blood cells, and a lower density componentsuch as plasma.

Among various blood component products obtainable through apheresis, thedemand for platelet products is rapidly growing. This is particularlybecause, with the improvement in cancer therapy, there is a need toadminister more and more platelets to patients with lowered hemopoieticfunction. Platelets are fragments of a large cell located in the marrowcalled a megakaryocyte and primarily contribute to hemostasis byperforming the aggregation function. Platelets also have a role intissue healing. Normal platelet counts are 150,000-400,000/mm³ in theadult. Platelet counts under 20,000/mm³ can cause various problems suchas spontaneous bleeding.

Platelets have a short half-life of 4-6 days and the number of donors islimited. Therefore, in producing plasma reduced platelet products, it isimportant to harvest platelets from the whole blood supplied by a donorat a maximum yield and in a required amount. Further, it is known thatthe contamination of plasma reduced platelet product by white bloodcells can lead to serious medial complications, such as GVH reactions.Therefore, it is also very important to keep the level of contaminationby white blood cells as low as possible, while efficiently collectingplatelets.

To that end, various techniques have been developed. For example, using“surge” technology, after whole blood is collected and concentricallyseparated within a centrifuge into higher density, intermediate densityand lower density components and plasma is harvested (so-called “draw”step), the plasma is supplied through the centrifuge at a surge flowrate, that is, a flow rate that increases with time. By performing thesurge, platelets can be preferentially displaced from the intermediatedensity components, which exist as a buffy coat mainly comprising amixture of platelets and white blood cells. Plasma reduced plateletproducts can thereby be produced at an increased yield.

Instead of using surge technology, the platelet layer can also beextracted from the centrifuge by means of a layer “push” in whichanticoagulated whole blood is introduced into the bowl until theplatelet layer is pushed out, or by using a combination of surge andpush methodologies. After harvesting a desired component or components,the residual blood components mostly comprising red blood cells arereturned to the donor (so-called “return” step).

Typically, 450-500 ml of whole blood is processed during one cycle whichcomprises the above-mentioned successive steps. This amount is based on15% or less of the total amount of blood in humans and, if more thanthis amount is taken out of the body at once, the donor may suffer fromblood pressure lowering or dizziness. Using surge technology, theconcentration of the sequestered platelet product ranges from 0.8×10⁶/μLto 2.6×10⁶/μL (typically 1.5×10⁶/μL), with moderate leukocyteconcentration. Pushed platelet product concentration tends to be higherbut leads to greater leukocyte and red blood cell residualcontamination.

This resulting platelet concentration is often too low for plateletproduct compatibility with arising pathogen inactivation methods.Additionally, simultaneous plasma collection of one to two additionalplasma units may be prevented due to the relatively high volume ofplasma captured with the platelet product. The relatively high plasmaprotein content in the platelet product is also less desirable in termsof recipient tolerance.

Blood processing systems, such as blood apheresis systems, add acitrated anticoagulant such as ACD-A to prevent blood and bloodcomponent clumping and coagulation within the system. Typically, theanticoagulant is mixed with the whole blood drawn from the donor. Theratio of anticoagulant to whole blood must be kept below a certainthreshold because most of the anticoagulant introduced into the systemwill be returned to the donor. If too much anticoagulant is returned tothe donor, the donor may experience adverse reactions such as a citratereaction.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a method forthe re-anticoagulation of platelet rich plasma in a blood apheresissystem includes collecting a volume of platelet rich plasma within afirst collection container, and adding anticoagulant into the firstcollection container as the platelet rich plasma is being collected. Thevolume of platelet rich plasma may be collected in a plurality ofcycles, and the anticoagulant may be added to the first collectioncontainer between each of the cycles. The method may also includepriming the blood apheresis system with anticoagulant such that a volumeof anticoagulant is transferred to the first collection container. Themethod may then transfer the anticoagulant within the first collectioncontainer to a second collection container.

In accordance with other embodiments, a method for there-anticoagulation of platelet rich plasma in a blood apheresis systemmay include drawing whole blood from a donor, introducing anticoagulantinto the whole blood, separating the anticoagulated whole blood into aplurality of blood components (including platelet rich plasma), andcollecting the platelet rich plasma in a collection container. Themethod may also add anticoagulant into the collection container as theplatelet rich plasma is collected. The volume of platelet rich plasmamay be collected in a plurality of cycles, and the anticoagulant may beadded to the collection container between each of the cycles. The methodmay also include priming the blood apheresis system with anticoagulantsuch that a volume of anticoagulant is transferred to the collectioncontainer. The method may then transfer the anticoagulant within thecollection container bag to a second container.

In accordance with further embodiment of the present invention, a methodfor the re-anticoagulation of platelet rich plasma in a blood apheresissystem includes priming the blood apheresis system with anticoagulantsuch that a volume of anticoagulant is transferred to a PRP collectioncontainer, and transferring the anticoagulant within the PRP collectioncontainer to a second container. The method then collects, in a numberof cycles, a volume of platelet rich plasma in the PRP collectioncontainer. Between cycles of the platelet rich plasma collectionprocess, the method transfers some of the anticoagulant from the secondcontainer to the PRP collection container. The amount of anticoagulanttransferred to the PRP collection container may be proportional to theamount of platelet rich plasma collected in the preceding cycle. Thetotal volume of anticoagulant transferred to the PRP collectioncontainer may be proportional to a target volume of platelet richplasma, which is the sum of the volumes collected in each of the cycles.

In accordance with other embodiments, the priming process may includepriming an anticoagulant line and a donor line filter withanticoagulant. The method may also transfer the anticoagulant within thedonor line filter to the second container (e.g., at the start of thefirst platelet rich plasma collection cycle) or the method may return itto an anticoagulant source.

Each of the platelet rich plasma collections cycles may include drawingwhole blood from a donor, introducing anticoagulant into the whole blooddrawn from the donor, and introducing the anticoagulated whole bloodinto a separation chamber. The separation chamber may separate theanticoagulated whole blood into a number of blood components includingplatelet rich plasma. The method may then extract the platelet richplasma from the separation chamber into the PRP collection container.The method may also reintroduce the collected platelet rich plasma intothe separation chamber, which separates the reintroduced platelet richplasma into plasma and plasma reduced platelet product. Once separated,the method may then extract the plasma reduced platelet product from theseparation chamber into a platelet container. The amount ofanticoagulant introduced into the whole blood upon withdrawal may beproportionately reduced by the volume of anticoagulant within the PRPcollection container.

In accordance with other embodiments of the present invention, a systemfor the re-anticoagulation of platelet rich plasma in a blood apheresissystem may include a PRP container for storing collected platelet richplasma, and a red blood cell container for storing red blood cells. Thesystem may also include means for priming the system with anticoagulantsuch that a volume of anticoagulant is transferred to the PRP container,and means for transferring the anticoagulant within the PRP container tothe red blood cell container. Additionally, the system may also havemeans for collecting a volume of platelet rich plasma within the PRPcontainer in a number of cycles, and means for transferring some or allof the volume of anticoagulant from the red blood cell container to thePRP container between each cycle. The volume of anticoagulanttransferred to the PRP container may be proportional to the amount ofplatelet rich plasma collected in the preceding cycle. The total volumeof anticoagulant transferred to the PRP container may be proportional toa target volume of platelet rich plasma, which is the sum of the volumescollected in each of the plurality of cycles.

The system may also prime an anticoagulant line and a donor line filterwith anticoagulant. The system may transfer the anticoagulant within thedonor line filter to the red blood cell container or the system mayreturn the anticoagulant within the donor line filter to ananticoagulant source. The means for transferring the anticoagulant maytransfer the anticoagulant within the donor line filter to the red bloodcell container at the start of the first of the plurality of cycles.

In accordance with still further embodiments, the system may alsoinclude means for drawing whole blood from a donor, means forintroducing anticoagulant into the whole blood drawn from the donor, andmeans for introducing the anticoagulated whole blood into a separationchamber. The separation chamber may separate the anticoagulated wholeblood into a number of blood components including platelet rich plasma.The system may then extract the platelet rich plasma from the separationchamber into the PRP container. The system may also have means forreintroducing the collected platelet rich plasma into the separationchamber, which further separates the reintroduced platelet rich plasmainto plasma and plasma reduced platelet product. The system may alsohave means for extracting the plasma reduced platelet product from theseparation chamber into platelet container. The amount of anticoagulantintroduced into the whole blood upon withdrawal may be proportionatelyreduced by the volume of anticoagulant within the PRP container.

In accordance with additional embodiments of the present invention, amethod for the re-anticoagulation of platelet rich plasma in a bloodapheresis system includes priming the blood apheresis system withanticoagulant such that a volume of anticoagulant is transferred to aPRP container, and collecting, in a number of cycles, a target volume ofplatelet rich plasma within the PRP container. The volume ofanticoagulant may be proportional to the target volume of platelet richplasma. The target volume may be the sum of the volumes collected ineach of the plurality of cycles.

Priming the blood apheresis system with anticoagulant may includepriming an anticoagulant line and a donor line filter withanticoagulant. The method may transfer the anticoagulant within thedonor line filter to the red blood cell container (e.g., at the start ofthe first cycle) or return it to an anticoagulant source. Each of thecycles may include drawing whole blood from a donor, introducinganticoagulant into the whole blood, and introducing the anticoagulatedwhole blood into a separation chamber. The amount of anticoagulantintroduced into the whole blood upon withdrawal may be proportionatelyreduced by the volume of anticoagulant within the PRP container.

The separation chamber may separate the anticoagulated whole blood intoa number of blood components including platelet rich plasma. The methodmay then extract the platelet rich plasma from the separation chamberinto the PRP container. After the cycles are complete and a targetvolume is collected, the method may reintroduce the platelet rich plasmafrom the PRP container into the separation chamber, which may furtherseparate the reintroduced platelet rich plasma into plasma and plasmareduced platelet product. The method may then extract the plasma reducedplatelet product from the separation chamber into a platelet container.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a system for use with an apheresismachine, in accordance with one embodiment of the invention;

FIG. 2 is a side view of a centrifuge bowl for use with the machine ofFIG. 1, in accordance with one embodiment of the invention;

FIG. 3 is a flow chart depicting a method for collecting platelet richplasma and plasma reduced platelet product, in accordance with oneembodiment of the invention;

FIG. 4 is a flow chart depicting a method for re-anticoagulatingcollected platelet rich plasma, in accordance with one embodiment of theinvention; and

FIG. 5 is a flow chart depicting an alternative method forre-anticoagulating collected platelet rich plasma, in accordance withone embodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to FIG. 1, an apheresis apparatus 10 uses a blood componentseparation device, such as a standard Latham type centrifuge 11 forseparating anticoagulated whole blood into its constituent components,as described in U.S. Pat. No. 3,145,713, which is hereby incorporated byreference. Other types of separation chambers and devices may be used,such as, without limitation, an integral blow-molded centrifuge bowl, asdescribed in U.S. Pat. Nos. 4,983,156 and 4,943,273, which are alsohereby incorporated by reference. The centrifuge 11 includes a rotatingbowl 12 and stationary input and output ports PT1 and PT2 that aretypically closely coupled to the bowl interior by a rotary seal 74 (seeFIG. 2). The input port PT1 of the centrifuge 11 is in fluidcommunication with a venous access devices 24 (e.g., a phlebotomyneedle) via, among other things, a blood filter F1, a tube 28 and aY-connector 30, when a valve V1 is open. The venous access device 24 maybe replaced with a whole blood bag (not shown) in case the whole bloodis to be first pooled and then supplied. The tube 28 has compatibilitywith blood, as is all the tubing in the apparatus 10. The outlet portPT2 of the centrifuge 11 is selectively coupled to a number ofcollection containers. For example, the centrifuge 11 may be selectivelycoupled to a platelet rich plasma bag 18 by a tube 36, a valve V2 and atube 37. The outlet port PT2 may also be selectively coupled to aplatelet container 20 via the tube 36, a valve V3 and a tube 39.Additionally, a plasma container 22 may also be selectively coupled tothe outlet port PT2 via the tube 36, a valve V4 and a tube 35. It isimportant to note that any of the above mentioned containers (e.g., theplatelet container 20, the plasma container 22, and the PRP container18) may be suspended by weight scales in order to help determine theamount of fluid within each of the containers.

A bag or container for storing an anticoagulant (not shown) may be influid communication with the venous access device/phlebotomy needle 24via a bacteria filter F2, a tube 32 and the Y-connector 30. The bacteriafilter F2 prevents any bacteria in the anticoagulant (ACD) containerfrom entering the system. Containers 18, 20, 22, and 23 are preferablyplastic bags made of a blood compatible material. Peristaltic pumps P1,P2 and P3, together with the valves V1, V2, V3, V4, V5, V6, V7, V8, andV9 control the direction and duration of flow through the apparatus 10in response to signals generated by a line sensor 14, a donor pressuremonitor (DPM) M1, a system pressure monitor (SPM) M2 and air detectorsD1, D2 and D3, which detect the absence or presence of fluid. Thepressure monitors M1 and M2 monitor pressure levels within the apparatus10. The line sensor 14 is an optical sensor and detects the presence ofblood components passing through the line sensor 14 from the output portPT2.

As described in greater detail below and with reference to FIGS. 4 and5, in initial operation, the pumps P1 and P3 are energized to prime thetube 28 of the apparatus 10 with the anticoagulant. The anticoagulantpasses through the filter F2 before reaching the air detector D1. Theair detector D1 senses the presence of the anticoagulant at D1 and mayterminate, advance, or alter the anticoagulant priming operation. Afterpriming, the venous access device 24 may be inserted into the donor andthe draw step is ready to be commenced.

FIG. 3 is a flowchart depicting a method for collecting blood components(e.g., platelets) from a subject, in accordance with one embodiment ofthe invention. During draw step 310, whole blood is drawn from thesubject, typically at a rate of about 80 ml/min. and mixed with theanticoagulant using the pumps P1 and P3 (referring back to FIG. 1) (Step320). The pump P3 introduces and mixes the anticoagulant with the wholeblood drawn from the subject (or from a bag in which it is pooled).During this time, the valve V1 is open, allowing the anticoagulatedwhole blood to pass through the tube 28 and blood filter F1 before beingpumped into the separation device 12 through the inlet port PT1.

The anticoagulated whole blood is introduced into the bottom of theseparation device 12 through a feed tube (not shown), step 330 of FIG.3. The ratio of the anticoagulant to whole blood is typically about1:10. However, as described in greater detail below, this ratio can beadjusted based upon the priming procedure used. The operation of each ofthe pumps and valves in the apheresis apparatus 10 can be performed inaccordance with desired protocols under the control of a controller (notshown), which may be, for example, a microprocessor.

As mentioned above and as shown in FIG. 2, the centrifuge 11 has a fixedinlet port PT1 and a fixed outlet port PT2. The rotary seal 74 fluidlycouples the stationary inlet port PT1 to the lower interior portion ofthe bowl 12, and the outlet port PT2 to an upper portion of the bowlinterior for collecting separated fractions. A core 72 occupies a volumecoaxial with the interior of bowl 12 and provides a separation regionbetween the wall of the core 72 and the outer bowl wall 70.

As the bowl 12 is rotated, centrifugal forces separate theanticoagulated whole blood introduced into the bottom of the bowl intored blood cells (RBC), white blood cells (WBC), platelets (e.g.,platelet rich plasma or “PRP”) and plasma. The number of rotations ofthe bowl 12 can be selected, for example, within a range of 4,000 to6,000 rpm, and is typically 4,800 rpm. The blood is separated intodifferent fractions in accordance with the component densities. Thehigher density component, i.e., RBC 60, is forced to the outer wall 70of the bowl 12 while the lower density plasma 66 lies nearer the core72. A buffy coat 61 is formed between the plasma 66 and the RBC 60. Thebuffy coat 61 is made up of an inner layer of platelets/PRP 64, atransitional layer 68 of platelets and WBC and an outer layer of WBC 62.The plasma 66 is the component closest to the outlet port from theseparation region and is the first fluid component displaced from thebowl 12 via the outlet port PT2 as additional anticoagulated whole bloodenters the bowl 12 through the inlet port PT1.

Returning to FIG. 1, the displaced plasma passes through the line sensor14, the tube 36, and a 4-way connector 26, and the valve V4 (in the openposition) and enters the plasma container 22. The plasma entering theplasma container 22 is drawn from the container 22 by the pump P2 viatube 42, valve V5 (in the open position), connector 92 and tube 40 fromthe lower port PT4 of the plasma container 22 and is recirculated intothe bowl 12 through the inlet port PT1 via connector 91 and line 41. Therecirculated plasma dilutes the anticoagulated whole blood entering thebowl 12 and allows the blood components to separate more readily. Anoptical sensor 21 is applied to a shoulder portion of the bowl 12 formonitoring each layer of the blood components as they gradually andcoaxially advance toward the core 72 from the outer wall 70 of the bowl12. The optical sensor 21 may be mounted in a position at which it candetect the buffy coat reaching a particular radius, and the steps ofdrawing the whole blood from the donor (Step 310) and introducing thewhole blood into the bowl (Step 330) may be terminated in response tothe detection.

The amount of whole blood processed by the bowl 12 may be varied inresponse to at least one characteristic associated with the whole blood,such as the hematocrit value, the number of platelets, the total amountof blood or the like of the whole blood, as described in U.S. Pat. No.6,743,192 issued Jun. 1, 2004 to Sakota et al. and entitled ApheresisApparatus and Method for Producing Blood Products, which is herebyincorporated by reference. This variable control can be implementedunder the control of a microcomputer, as aforementioned. Alternatively,each of them can be implemented manually.

The platelets (e.g., platelet rich plasma or “PRP”) are extracted fromthe bowl 12 into a PRP container 18, step 340 of FIG. 3. In extractingthe platelet rich plasma (“PRP”) from the bowl, various methodologiesmay be employed, including, without limitation, dwell, surge, and/orpush methodologies. For illustrative purposes, PRP extraction based on adwell and surge technique will now be described in detail.

After the anticoagulated whole blood has been introduced into thecentrifuge 11, step 330 of FIG. 3, the valve V1 is closed and the pumpP1 is stopped so that blood is no longer drawn from the donor, and dwellis commenced. During the dwell, the pump P2 recirculates plasma 66through the bowl 12 at a moderate rate (for example, about 100 ml/min.in FIG. 4) for about 20 to 30 seconds. At this flow rate, the buffy coat61 is diluted by the plasma and widens but the platelets/PRP do notleave the bowl 12. The dilution of the buffy coat allows the heavierwhite blood cells to sediment to the outer side of the buffy coat,resulting in a better separation between the lighter platelet/PRP layer64 and the heavier white blood cells layer 62. As a result, thetransitional layer 68 is reduced. The dwell period also allows the flowpatterns in the bowl 12 to stabilize and allows more time formicrobubbles to leave the bowl 12 and be purged.

After dwell, the surge step is commenced. In the surge, the speed of thepump P2 is increased in 5-10 ml/min. increments to recirculate plasmauntil reaching a platelet/PRP surge velocity of about 200-250 ml/min.The platelet/PRP surge velocity is the velocity at which platelets/PRPcan leave the bowl 12 but not red blood cells or white blood cells. Theplasma exiting the bowl 12 becomes cloudy with platelets/PRP and theline sensor 14 detects this cloudiness. The line sensor 14 consists ofan LED which emits light through the blood components leaving the bowl12 and a photo detector which receives the light after it passes throughthe components. The amount of light received by the photo detector iscorrelated to the density of the fluid passing through the line.

When platelets/PRP first start leaving the bowl 12, the line sensoroutput starts to decrease. The valve V2 is opened and the valve V4 isclosed and the platelets/PRP are collected in container 18. Once themajority of the platelets/PRP are removed from the bowl 12, the fluidexiting the bowl becomes less cloudy. The line sensor 14 detects thislessening of cloudiness, whereupon valve V2 is closed.

After the platelets/PRP have been collected, return step 350 (see FIG.3) is initiated. During return step 350, the rotation of the bowl 12 isstopped and the remaining blood components in the bowl 12 are returnedto the donor by reversal of rotation of the pump P1 via the venousaccess device 24 with the valve V1 open. The valve V4 is also opened toallow air to enter the centrifuge bowl during the return. The plasmafrom the container 22 dilutes the remaining blood components in the bowl12. In other words, the pump P2 mixes the plasma with the returningcomponents in the bowl 12 with the valve V4 open, thereby diluting thereturning red blood cells component with plasma and speeding up thereturn time. When the remaining blood components in the bowl have beenreturned to the donor, the return step 350 is terminated.

The steps of drawing whole blood from the donor, step 310, introducinganticoagulant into the whole blood, step 320, introducing the wholeblood into a separation chamber, step 330, extracting platelets/PRP fromthe separation chamber into a container, step 340, and returning theremaining components back to the donor, step 350, are repeated until atarget volume of platelets/PRP is sequestered in the container 18, step360. Typically, steps 310-350 are repeated two to four times, with about450-500 ml of whole blood processed per cycle. The sequesteredplatelet/concentration within the PRP is typically about 1.5×10⁶/μL.

The method 300 may then reintroduce the platelets/PRP in container 18into the bowl 12, step 370 of FIG. 3, forming a layer of platelets/PRPthat is several times larger than that obtained by processing only onecycle of whole anticoagulated blood. For example, in some embodiments,the platelet/PRP layer volume is approximately equal to the averagevolume of one cycle multiplied by the number of platelet/PRPsequestering cycles plus one. The platelets/PRP are drawn from port PT5of container 18 by pump P2 via tube 43, valve V7 (in the open position),connector 93, and input into bowl 12 through the inlet port PT1 viaconnector 91 and line 41. To minimize contact between the platelets/PRPand bowl 12, the bowl 12 may be partly filled with anticoagulated wholeblood drawn from the donor prior to re-introduction of the platelets.The whole blood forms a cell bed at the periphery of the bowl 12 thatserves as a buffer between the periphery of the bowl and theplatelets/PRP, reducing platelet clumping. Additionally oralternatively, whole anticoagulated blood may be added to the separationchamber during platelet/PRP reintroduction so as to bring platelet layertowards the elutriation radius, or after platelet/PRP reintroduction forperfecting platelet separation and standardizing conditions ofinitiating platelet extraction.

Using, for example, surge or push methodologies, a plasma reducedplatelet product is extracted from the layer of platelets that nowreside in bowl 12, step 380 of FIG. 3. The plasma reduced plateletproduct is sequestered in container 20 via line sensor 14, tube 36,connector 26, connector 50, and valve V3 (in the open position).Platelet product concentration is typically in the range of 2.6×10⁶/μLto 5.2×10⁶/μL, which is 2-3 times that of platelets/PRP sequestered whenprocessing only one cycle of whole anticoagulated blood.

It is important to note that during the reprocessing of the PRPcollected within the PRP container 18, the platelets/PRP that arereintroduced into the separation chamber may begin to coagulate and/orclump. In order to prevent clumping and coagulation, additionalanticoagulant may be added to platelets/PRP prior to reprocessing withinthe separation chamber 12. However, care must be taken to avoid addingtoo much anticoagulant because, as discussed above, if too muchanticoagulant is returned to the donor, the donor may experiencenegative side effects. Accordingly, embodiments of the present inventionutilize the initial priming step discussed above to provide the PRP withadditional anticoagulant while avoiding adding additional anticoagulantto the overall system 10. FIGS. 4 and 5 show exemplary embodiments ofsuch methods.

As shown in FIG. 4, the blood apheresis method 400 begins with primingthe apheresis system, step 410. During the priming step, pumps P1 and P3prime the anticoagulant line 32 and the donor line 28 until theanticoagulant is detected by D2. The system 10 will then continuepriming the system until the donor line 28 is full of anticoagulant anda small amount of anticoagulant is transferred into the PRP container 18via line 28, valve V1, pump P1, connector 93, line 43, and valve V7. Theamount of anticoagulant transferred into the PRP container 18 may beproportional to the expected volume of PRP to be collected using thetechniques described above (e.g., it may be proportional to the targetvolume of PRP). For example, the volume of anticoagulant within the PRPcontainer 18 may be 1/10^(th) of the target PRP volume (e.g., if thetarget PRP volume is 300 ml, 30 ml may be transferred into the PRPcontainer 18).

Once the system 10 is primed with anticoagulant and the desired amountof anticoagulant is within the PRP container 18, the system 10 may beginto collect the platelets/PRP (step 420), as described above with regardto FIG. 3 (e.g., the system 10 may collect the platelets/PRP using thedraw, separate, and extract cycles shown in FIG. 3). As theplatelets/PRP are extracted from the separation chamber 12, they willenter the PRP container 18 containing the additional anticoagulant andmix with the anticoagulant.

It should be understood that the initial concentration of anticoagulantwithin the PRP container 18 will be higher than the target finalconcentration (e.g., 1:10). However, as the system 10 collectsadditional platelets/PRP in each subsequent cycle, the anticoagulantconcentration will decrease towards the final concentration levelbecause, as mentioned above, the amount of anticoagulant added to thePRP container 18 may be proportional to the target volume of PRP. Theprocess 400 may continue until the target volume of platelets/PRP iscollected (step 430).

FIG. 5 shows an alternative embodiment of the priming process shown inFIG. 4. In this embodiment, the anticoagulant may be metered into thePRP container 18 as additional collection cycles are completed. Inparticular, once the system 10 is primed with anticoagulant and the PRPcontainer 18 has the desired amount of anticoagulant (e.g., as discussedabove) (Step 410), the system 10 may then transfer the anticoagulant inthe PRP container 18 to the RBC container 23 (Step 510). Thesystem/method 500 may transfer the anticoagulant within the PRPcontainer 18 to the RBC container 23 using pump P1, which will transferthe anticoagulant to the RBC container 23 through valve V7 (open), line43, connector 93, valve V9 (open), and line 49.

The system 10 may then begin to collect the platelets/PRP as describedabove and as shown in FIG. 3 (Step 420). If the anticoagulant primeended with filter F1 full of anticoagulant, the system 10 may start thefirst draw cycle by transferring the anticoagulant within filter F1 tothe RBC container 23 or back to the anticoagulant source. As discussedin greater detail below, if the anticoagulant is transferred to the RBCcontainer, this volume should be taken into account when determining thecorrect amount of anticoagulant. In accordance with embodiments of thepresent invention, a portion of the anticoagulant within the RBCcontainer 23 may be transferred to the PRP container 18 between thecollection cycles (Step 520). For example, after the first cycle ofplatelets/PRP is collected, the system 10 may transfer a portion of theanticoagulant to the PRP container 18. In particular, the draw cyclewill start by transferring a portion of the volume within the RBCcontainer 23 to the PRP bag using pump P1 and pump P2 (e.g., in series).If the pump tubing segments contains blood from the prior cycle, thepump P1 will transfer the blood to the separation device 12 prior totransferring the anticoagulant to the PRP container 18.

As the system 10 approaches the end of the anticoagulant transfer (Step520), pump P1 will start drawing the whole blood from the donor to startthe next draw/collection cycle. Since the anticoagulant transfer may notyet be complete, the beginning of the next draw phase will finish theanticoagulant transfer to the PRP container 18 before the anticoagulatedwhole blood is directed to the bowl.

The amount of anticoagulant added to the PRP container 18 after eachcycle may be proportional to the amount of platelets/PRP collectedduring the preceding or subsequent cycles. For example, if the totalvolume to be transferred into the PRP container is 30 ml (e.g., toachieve the 1:10 ratio with the target volume of collected PRP), and theplatelets/PRP are collected in 5 cycles, 6 ml of anticoagulant may beadded to the PRP container 18 after each cycle. This allows the systemto provide sufficient anticoagulant to avoid platelet/PRPclumping/coagulation and avoid an initial high concentration ofanticoagulant. The process 500 may continue until the target volume ofplatelets/PRP is collected (step 430). Although, the methods/system usethe RBC container 23 to store the anticoagulant between cycles, once theanticoagulant is fully transferred to the PRP container 18 (e.g., afterthe last collection cycle), the RBC container 23 may be used forrecovering pre-filter red blood cells in preservative solution.

It is important to note that, because valve V1 is closed during thetransfer of anticoagulant from the PRP container 18 to the RBC container23 (e.g., Step 510 in FIG. 5), a significant amount of anticoagulant mayremain in the filter F1 (e.g., from the initial prime step). Some or allof this anticoagulant may either be transferred back to theanticoagulant source or it may be transferred to the RBC container 23.If the anticoagulant is transferred to the RBC container 23, the amountof anticoagulant should be taken into account when determining the totalamount of anticoagulant within the system (e.g., to ensure that too muchanticoagulant is not being return to the donor) and determining theamount of anticoagulant needed to re-anticoagulate the PRP. If theanticoagulant is returned to the anticoagulant source, it need not betaken into account.

Although the above described embodiments meter anticoagulant into thePRP container 18 in bolus transfers (e.g., either during the initialprime or between cycles of collecting the PRP), other embodiments of thepresent invention may continuously meter anticoagulant into the PRPand/or PRP container 18 as the system 10 collects the PRP. In otherwords, embodiments of the present invention may, as PRP is beingextracted from the bowl 12, introduce anticoagulant into the PRP or thePRP container 18 in a manner similar to the way the system 10 introducesthe anticoagulant into the whole blood as it is withdrawn from the body.

To facilitate the addition of anticoagulant directly into the PRP as itis being extracted from the bowl 12, the system 10 may have additionalvalving, pumps, and connectors. For example, line 36 may have anadditional connector located between the line sensor 14 and the PRPcontainer 18. This connector may be used to connect the anticoagulantsource with the line 36 using an additional line. If needed, theadditional line may have an additional pump to help transfer/introducethe anticoagulant into the PRP. The anticoagulant may then be introducedinto the PRP as it passes through line 36.

Other embodiments, as mentioned above, may continuously meter theanticoagulant for the PRP directly into the PRP container 18. Tofacilitate this addition, the system 10 may have an additionalconnector, valve, pump, and line that connect to line 43 (e.g., in amanner similar to that described above for embodiments continuouslymetering anticoagulant into the PRP as it passes through line 36). Thisconfiguration allows the anticoagulant to be added to the PRP container18 via port PT5.

It is also important to note that, because the above describedre-anticoagulation methods add the additional anticoagulant directly tothe platelets/PRP, embodiments of the present invention do not need toadd additional anticoagulant to the overall system 10 (e.g., by addingadditional anticoagulant to the whole blood as it is drawn from thedonor). In order to achieve the same benefits of the embodiments of thepresent invention, systems adding anticoagulant to the overall systemwill ultimately return an additional 153 ml of anticoagulant to thedonor. In other words, in order to achieve the additional 30 ml requiredfor re-processing the platelets/PRP to obtain the plasma reducedplatelet product, the ratio of anticoagulant will need to increase from1:9 to 1:6.1, as compared to embodiments of the present invention.Accordingly, by using the above described methods, the risk of returningtoo much anticoagulant to the patient is greatly reduced.

It should be noted that the surge elutriation technique may use avariety of fluids other than plasma to extract either the platelets/PRPor the reduced plasma platelet product from the separation chamber(e.g., saline solution may be used).

Additionally, once the platelets and the reduced plasma platelet productare collected, a platelet additive/preservative solution may be added tohelp preserve and store the platelets for later use. The preservativesolution can be added to the reduced plasma platelet product within theplatelet container 20 after collection, or the platelet collection bag20 and the reduced plasma platelet product bag 22 may be pre-loaded withthe additive solution. To facilitate the addition of additive solution,the system 10 may include a platelet additive storage container (notshown) and a platelet additive line 45 that may be fluidly connected toplatelet bag 20 via connector 46, and line 47. In a similar manner tothe other lines and tubes within the system, the platelet additive line45 may also include a valve V6 that prevents/allows flow through theplatelet additive line 45. Such embodiments may also have a line 48fluidly connecting a platelet storage bag 70 and the reduced plasmaplatelet product bag 20. This line may include a valve V8 and a filterF3, such as a leukoreduction filter. Once the additive solution isadded, the system 10 may transfer the plasma reduced platelet product tothe platelet storage container 70 for storage.

If additional reduced plasma platelet product is required, each of thesteps described above (e.g., 310-380 and 410-430) may be repeated untila desired quantity of plasma reduced platelet product is collected. Invarious embodiments, plasma may be added to the plasma reduced plateletproduct so as to adjust the plasma reduced product to a predeterminedvolume or concentration.

It is important to note that some embodiments of the apheresis apparatuscan be three-line systems having, in addition to some or all of thecomponents discussed above, a dedicated return line, and a dedicateddraw line. In such embodiments, both the return line and the draw linemay have a dedicated pump that controls the flow and pressure within thelines. For example, the return line may have a dedicated return pump andthe draw line may have a dedicated draw pump. In addition to thededicated pumps, each line may also include a pressure sensor thatallows the system to monitor the pressure within the lines and adjustthe flow rate based on the pressure measurements.

The described embodiments of the invention are intended to be merelyexemplary and numerous variations and modifications will be apparent tothose skilled in the art. All such variations and modifications areintended to be within the scope of the present invention.

We claim:
 1. A method for the re-anticoagulation of platelet rich plasmain a blood apheresis system, the method comprising: priming the bloodapheresis system with anticoagulant such that a volume of anticoagulantis transferred to a PRP container, the volume of anticoagulant beingproportional to a target volume of platelet rich plasma, wherein primingincludes drawing anticoagulant from an anticoagulant source and througha line fluidly connecting the anticoagulant source and the PRPcontainer; and collecting the target volume of platelet rich plasmawithin the PRP container.
 2. A method according to claim 1, whereinpriming the blood apheresis system with anticoagulant further includespriming an anticoagulant line and a donor line filter withanticoagulant.
 3. A method according to claim 2, wherein priming theblood apheresis system further includes transferring the anticoagulantwithin the donor line filter to a red blood cell container.
 4. A methodaccording to claim 3, wherein the target volume of platelet rich plasmais collected in a plurality of cycles, the anticoagulant within thedonor line filter transferred to the red blood cell container at thestart of a first of the plurality of cycles.
 5. A method according toclaim 3, wherein the anticoagulant within the donor line filter isreturned to an anticoagulant source.
 6. A method according to claim 1,wherein the target volume of platelet rich plasma is collected in aplurality of cycles.
 7. A method according to claim 6, wherein thetarget volume is the sum of the volumes collected in each of theplurality of cycles.
 8. A method according to claim 6, wherein each ofthe plurality of cycles includes: drawing whole blood from a donor;introducing anticoagulant into the whole blood drawn from the donor;introducing the anticoagulated whole blood into a separation chamber,wherein the separation chamber separates the anticoagulated whole bloodinto a number of blood components including platelet rich plasma; andextracting the platelet rich plasma from the separation chamber into thePRP container.
 9. A method according to claim 1, further comprising:reintroducing the platelet rich plasma from the PRP container into theseparation chamber, the separation chamber separating the reintroducedplatelet rich plasma into plasma and plasma reduced platelet product;and extracting the plasma reduced platelet product from the separationchamber into a platelet container.
 10. A method according to claim 1,wherein an amount of anticoagulant introduced into the whole blood isproportionately reduced by the volume of anticoagulant within the PRPcontainer.